1. Technical Field
The present inventions relate to charge pumps and, more particularly, relate to negative charge pump regulation.
2. Description of the Related Art
A paper by Bloch, M., Lauterbauch, C., and Weber, W., entitled High Efficiency charge Pump Circuit for Negative High Voltage Generation at 2 V Supply Voltage, presented at the Solid-State Circuits Conference, 1998. ESSCIRC '98. Proceedings of the 24th European, 22-24 Sep. 1998, pages 100-103 discloses voltage division along with a bypass path approach for a negative pump.
U.S. Pat. No. 7,554,311 by Pan and granted on Jun. 30, 2009 discloses regulation for a positive charge pump. The continuous time domain portion of this hybrid scheme uses voltage division as opposed to imposing a fixed IR drop and the high frequency sampling component relies on capacitor division. This prior patent attempts to combine two known regulation techniques. This approach becomes awkward when trying to regulate multiple levels.
These previous approaches fail to solve continuous time average sampling as well as high frequency response simultaneously for a negative charge pump.
The present invention is illustrated by way of example and is not limited by the accompanying figures, in which like references indicate similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale.
The details of the preferred embodiments will be more readily understood from the following detailed description when read in conjunction with the accompanying drawings wherein: